Replenishing power supply system

ABSTRACT

In a replenishing power supply system, a plurality of DC/DC converters ( 5, 6  and  7 ) are connected in parallel, and the number of DC/DC converters ( 5, 6  and  7 ) to be started is changed based on the amounts of electric power used by auxiliary loads ( 11  and  12 ). Moreover, the DC/DC converters ( 5, 6  and  7 ) are started in order based on a predetermined sequence.

TECHNICAL FIELD

[0001] The present invention relates to an improvement of a replenishingpower supply system having both a main power supply and an auxiliarybattery.

BACKGROUND ART

[0002] As a replenishing power supply system having a main power supplyand an auxiliary battery, a fuel cell vehicle ACV) or the like using afuel cell as a main power supply and a secondary cell as an auxiliarybattery described in Japanese Patent Application Laid-Open No.2001-28807 has been known.

DISCLOSURE OF THE INVENTION

[0003] Generally, a voltage of electric power from a main power supplyis converted by a DC/DC converter, and then supplied to an auxiliarybattery or an auxiliary load. In the case of handling a large current, alarge-capacity DC/DC converter is necessary. However, considering that acapacity of harness is also increased and so on, it is often practicalto connect a plurality of DC/DC converters in parallel to one auxiliarybattery.

[0004] In such a case, starting/stopping operations of the plurality ofDC/DC converters are carried out by one signal (these operations arecalled parallel operations), and all the DC/DC converters are always runsimultaneously. Then, if there is variance in voltage-currentcharacteristics of the plurality of DC/DC converters, when run by thesame voltage, a frequency of use (the frequency of use is equivalent toan accumulation of loads or currents) of a DC/DC converter having alargest current becomes higher compared with those of the other DC/DCconverters. Therefore, the DC/DC converter having a high frequency ofuse becomes shorter in life compared with the other DC/DC converters. Ifit is defined that a system comes to an end of its life when one DC/DCconverter reaches its life, dependence is placed on the DC/DC converterhaving a highest frequency of use, whereby system life is shortened.

[0005] Moreover, reuse as a system is allowed by replacing only theDC/DC converter that has reached its life. However, problems have beeninevitable, such as necessity of time and labor for replacingcomponents, and an increase in costs caused by necessity of componentsfor replacement.

[0006] The fist aspect of the present invention provides a replenishingpower supply system for supplying electric power to a load, thereplenishing power supply system comprising: a main power supply; aplurality of DC/DC converters for converting the electric power from themain power supply and outputting the electric power; and an auxiliarybattery for charging the electric power converted by the plurality ofDC/DC converters, wherein the plurality of DC/DC converters areconnected in parallel, wherein the number of DC/DC converters to bestarted is changed according to an amount of the electric power used bythe load, and wherein based on a predetermined starting sequence, theDC/DC converters are started in order.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a configuration view of a replenishing power supplysystem for a vehicle according to a first embodiment of the presentinvention;

[0008]FIGS. 2A and 2B are examples showing voltage-currentcharacteristics of DC/DC converters of the first embodiment;

[0009]FIG. 3 is a flowchart showing control outline of the firstembodiment;

[0010]FIG. 4 is a configuration view of a vehicle replenishing powersupply system according to a second embodiment of the present invention;

[0011]FIG. 5 is a flowchart showing control outline of the secondembodiment;

[0012]FIG. 6 is a time chart showing an operation of the secondembodiment;

[0013]FIG. 7 is a configuration view of a vehicle replenishing powersupply system according to a third embodiment of the present invention;

[0014]FIG. 8 is a flowchart showing control outline of the thirdembodiment;

[0015]FIG. 9 is a time chart showing an operation of the thirdembodiment; and

[0016]FIG. 10 is a flowchart showing control outline according to afourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT TIE INVENTION

[0017] Hereinafter, detailed description will be made of the presentinvention by way of preferred embodiments with reference to theaccompanying drawings.

[0018] (First Preferred Embodiment)

[0019]FIG. 1 is a configuration view of a replenishing power supplysystem of a first embodiment, which shows a vehicle replenishing powersupply system to which the present invention is applied.

[0020] Three DC/DC converters 5 to 7 convert voltage of electric powerfrom a main power supply 17 constituted by a fuel cell or the like. TheDC/DC converters 5 to 7 are connected in parallel, and output electricpower of each of the DC/DC converters 5 to 7 is supplied through each offuses F/L2 to F/L4 to an auxiliary battery 1.

[0021] A control unit C/U 8 for outputting an operation command to eachDC/DC converter is connected to the DC/DC converters 5 to 7, by whichthe electric power from the main power supply is converted according tothe operation command.

[0022] Relays 9 and 10 are connected in parallel from the auxiliarybattery 1. These relays are connected so as to continue electric powerto auxiliary loads 11 and 12 by the command of the control unit C/U 8.The electric power converted by the DC/DC converters 5 to 7 is used forcharging the auxiliary battery, and is used as a power supply foroperating the auxiliary loads.

[0023] An ignition switch IGN 18 converts an operation of an ignitionkey by a driver into a signal.

[0024] Here, description will be made for operations of the DC/DCconverters when voltage-current characteristics of individual outputs ofthe DC/DC converters 5 to 7 exhibit states similar to those of FIG. 2A

[0025] When the three DC/DC converters 5 to 7 are simultaneouslyoperated, a voltage is converted only by the DC/DC 5 if a total load iswithin 50A.

[0026] If a total load is within the range from 50A to 100A, the DC/DC 5continues its voltage conversion at 50A, and the DC/DC 6 converts avoltage in the range of 0A to 50A.

[0027] If a total load is within the range from 100A to 150A, the DC/DC5 and the DC/DC 6 continue voltage conversion at 50A, and the DC/DC 7converts a voltage in the range of 0A to 50A.

[0028] Next, description will be made for operations of the DC/DCconverters when voltage-current characteristics of individual outputs ofthe DC/DC converters 5 to 7 exhibit states similar to those of FIG. 2B.

[0029] When the three DC/DC converters 5 to 7 are simultaneouslyoperated, a voltage is converted only by the DC/DC 5 if a total load iswithin 25A (the voltage at which only the DC/DC 5 is operated).

[0030] If a total load is within the range from 25A to 75A (in therange, a corresponding voltage at which the DC/DC S and the DC/DC 6 areoperated), the DC/DC 5 converts a voltage in the range of 25A to 50A,and the DC/DC 6 in the range of 0A to 25A.

[0031] If a total load is within the range from 75A to 100A, the DC/DC 5continues its voltage conversion, and the DC/DC 6 converts a voltage inthe range of 25A to 50A.

[0032] If a total load is within the range from 100A to 150A, the DC/DC5 and the DC/DC 6 continue voltage conversion, and the DC/DC 7 convertsa voltage in the range of 0A to 50A.

[0033] Accordingly, by connecting the DC/DC converters 5 to 7 inparallel at all times, and simultaneously using them, the DC/DCconverter 5 having a high conversion voltage always executes voltageconversion. Thus, a frequency of use (i.e., operation time) of the DC/DCconverter S becomes high, thereby causing the DC/DC conductor S to reachits life earlier than the DC/DC converters 6 and 7.

[0034] Therefore, according to the present embodiment, the DC/DCconverters 5 to 7 are started one by one in order based on apredetermined starting sequence according to the amount of electricpower used by the load, and the starting sequence is changed based on aregulated sequence, thus dispersing frequencies of use of the DC/DCconverters 5 to 7.

[0035] Hereinafter, a control operation regarding a start is described.

[0036] As a predetermined starting sequence, three patterns are providedas follows:

[0037] Pattern 1=DC/DC5→DC/DC6→DC/DC7

[0038] Pattern 2=DC/DC6→DC/DC7→DC/DC5

[0039] Pattern 3=DC/DC7→DC/DC5→DC/DC6

[0040] As the regulated sequence for changing the starting sequence, thepatterns are changed in a manner of 1→2→3→1 for each changing of theignition switch (IGN) from OFF to ON, i.e., for each turning ON (IGNON).of the vehicle ignition key.

[0041]FIG. 3 is a flowchart showing outline of control mainly carriedout at the control unit C/U 8.

[0042] In step S1, determination is made as to whether this process isthe first process after IGN ON. If it is the first process, a startingsequence is set in steps S2 to S5. In step S2, determination is made asto which of the patterns 1 to 3 is a previous pattern of the startingsequence belongs to. According to the pattern, the process proceeds tosteps S3 to S5, and a current pattern of the starting sequence isdecided. In step 56, load states (i.e., demanded electric power) of theauxiliary loads 11 and 12 are detected. In step S7, the number of DC/DCconverters to be operated is decided according to the load states of theauxiliary loads 11 and 12. Further, the DC/DC converters are startedaccording to the set pattern of the starting sequence.

[0043] Operations of the auxiliary loads 11 and 12 can be controlled bythe C/U 8. Thus, electric power consumptions of the auxiliary loads 11and 12 are memorized in the C/U 8, and the number of DC/DC converters tobe operated is changed according to operating states (i.e., electricpower using states) of the auxiliary loads 11 and 12. When the DC/DCconverters are stopped, they are stopped in order inverse to that of thestarting time.

[0044] In the first embodiment, the starting sequence was changed foreach IGN ON. However, the changing is not limited to such, and thestarting sequence may be changed for every several IGN ON and the like.

[0045] (Second Preferred Embodiment)

[0046]FIG. 4 shows a configuration of a second embodiment. Only portionsdifferent from those of the first embodiment will be described, anddescription of common portions will be omitted.

[0047] In addition to the configuration of the first embodiment, voltagedetecting means 13 is provided in the auxiliary battery 1.

[0048] In the embodiment, a predetermined starting sequence is setaccording to a relation of voltage characteristics in voltage-currentcharacteristics of each DC/DC converter (magnitude relation of outputvoltages when the same current is taken out).

[0049]FIG. 5 is a flowchart showing control in outline. In the control,setting of a starting sequence is carried out only when IGN ON is thefirst time (first after vehicle manufacturing), and on a specific mode(on repairing/inspection).

[0050] In step S21, determination is made as to whether IGN ON is thefirst time (first after vehicle manufacturing). Further, in step S22,determination is made as to whether the process is on a specific mode(on repairing/inspection).

[0051] In step S23, if either one of steps S21 or S22 is YES, theauxiliary loads 11 and 12 are stopped.

[0052] In step S24, a starting command is executed to the DC/DCconverter 5. A voltage of the auxiliary battery 1 at this time isdetected by the voltage detecting means 13, and sent the voltage to theC/U 8. Then, the DC/DC converter 6 is started after a fixed period(about 1 sec.). A voltage of the auxiliary battery 1 at this time isdetected by the voltage detecting means 13, and sent the voltage to theC/U 8. Then, the DC/DC converter 7 is started after a fixed period(about 1 sec.). A voltage of the auxiliary battery 1 at this time isdetected by the voltage detecting means 13, and the voltage is sent tothe C/U 8.

[0053] In step S25, based on the voltage changes detected in step S24, amagnitude relation in voltage characteristics (i.e., conversion voltage)among the DC/DC converters 5 to 7 is acquired. Here, a voltage detectedby the voltage detecting means 13 becomes a voltage of a DC/DC converterhaving a highest voltage characteristics among the plurality of DC/DCconverters being operated. Thus, in the case of voltage characteristicsof magnitude relations similar to those of FIGS. 2A and 2B, V5>V6, andV5>V7 are determined in this step, while a relation between V6 and V7 isnot clear (V5, V6 and V7 respectively represent output voltages at theDC/DC converters 5, 6 and 7. The same holds true in the following).

[0054] In step S26, stopping commands are executed from the C/U 8 to theDC/DC converters 5 to 7.

[0055] In step S27, first, a starting command is executed from the C/U 8to the DC/DC converter 6. A voltage of the auxiliary battery 1 at thistime is detected by the voltage detecting means 13, and sent the voltageto the C/U 8. Then, the DC/DC converter 7 is started after a fixedperiod (about 1 sec.). A voltage of the auxiliary battery 1 at this timeis detected by the voltage detecting means 13, and the voltage is sentto the C/U 8. Then, the DC/DC converter S is started after a fixedperiod (about 1 sec.). A voltage of the auxiliary battery 1 at this timeis detected by the voltage detecting means 13, and the voltage is sentto the C/U 8.

[0056] In step S28, based on the voltage changes detected in step S27, amagnitude relation in voltage characteristics (i.e., the conversionvoltage) among the DC/DC converters 5 to 7 is acquired. (V6>V7, V5>V7,and V5>V6).

[0057] In step S29, stopping commands are executed again from the C/U 8to the DC/DC converters 5 to 7.

[0058] In step S30, first, a starting command is executed from the C/U 8to the DC/DC converter 7. A voltage of the auxiliary battery 1 at thistime is detected by the voltage detecting means 13, and the voltage issent to the C/U 8. Then, the DC/DC converter 5 is started after a fixedperiod (about 1 sec.). A voltage of the auxiliary battery 1 at this timeis detected by the voltage detecting means 13, and the voltage is sentto the C/U 8. Then, the DC/DC converter 6 is started after a fixedperiod (about 1 sec.). A voltage of the auxiliary battery 1 at this timeis detected by the voltage detecting means 13, and the voltage is sentto the C/U 8.

[0059] In step S31, based on the voltage changes detected in step S30, amagnitude relation in voltage characteristics (i.e., the conversionvoltage) among the DC/DC converters 5 to 7 is acquired. (V5>V7, andV5>V6, but the magnitude relation between V6 and V7 is not clear).

[0060] Incidentally, FIG. 6 shows a relation between the operation ofthe DC/DC converter and the change of voltage in steps S24 to S30.

[0061] In step S32, based on the results of steps S25, S28 and S31, amagnitude relation in- voltage characteristics (V5>V6>V7 in thisexample) among the three DC/DC converters 5 to 7 is acquired. Then, astarting sequence after a normal starting time is set in the order ofsmall voltage characteristics (DC/DC7→DC/DC6→DC/DC5 in this example).

[0062] Steps S33 and S34 are similar to steps S6 and S7 of the firstembodiment.

[0063] Therefore, a frequency of use of a DC/DC converter having a smallvoltage characteristics becomes large at the time of starting. However,when a load becomes large, and the plurality of DC/DC converters areoperated, a load of the DC/DC converter having a small voltagecharacteristics becomes small, so that deviation in frequencies of usecan be canceled. Accordingly, life deviation among the converters canalso be canceled, whereby a life of the replenishing power supply systemis prolonged.

[0064] In the second embodiment, voltage characteristics of the DC/DCconverters are measured after they are mounted on the vehicle. However,the measurement is not limited to this. For example, voltagecharacteristics of the DC/DC converters may be measured before they aremounted on the vehicle, and then a starting sequence may be storedbeforehand in the C/U 8 based on a magnitude relation of the voltagecharacteristics. In such a case, the steps S21 to S32 described abovecan be abbreviated.

[0065] (Third Preferred Emb diment)

[0066]FIG. 7 shows a configuration of a third embodiment. Only portionsdifferent from those of the first and second embodiments will bedescribed, and description of common portions will be omitted.

[0067] In addition to the configuration of the first embodiment, currentdetecting means 14 to 16 are provided in the DC/DC converters 5 to 7,respectively.

[0068] In the present embodiment, a predetermined starting sequence isset according to a relation of current characteristics involtage-current characteristics of each DC/DC converter (a magnituderelation among output currents when the same voltage is outputted).

[0069]FIG. 8 is a flowchart showing control in outline.

[0070] In the control, as is the case of the second embodiment, settingof a starting sequence is carried out only at first IGN ON (first aftervehicle manufacturing), and on a specific mode (onrepairing/inspection).

[0071] Steps S41 to S43 are similar to steps S21 to S23 of the secondembodiment.

[0072] In step S44, first, a starting command is executed to the DC/DCconverter 5. A current of the DC/DC converter 5 at this time is detectedby the current detecting means 14, and the current is sent to the C/U 8.Then, the DC/DC converter 6 is started after a fixed period (about 1sec.). A current of the DC/DC converter 6 at this time is detected bythe current detecting means 15, and the current is sent to the C/U 8.Then, the DC/DC converter 7 is started after a fixed period (about 1sec.). A current of the DC/DC converter 7 at this time is detected bythe current detecting means 16, and the current is sent to the C/U 8.

[0073] In step S45, based on the current changes detected in step S44, amagnitude relation in current characteristics (magnitude of currents atthe same voltage) among the DC/DC converters 5 to 7 is acquired.

[0074] As described above, if a load is low, a current only flows to aDC/DC converter having a large current characteristics. Thus, in thecase of current characteristics of magnitude relations similar to thoseof FIGS. 2A and 2B, I5>I6, and I5>I7 are revealed in this step S45,while a magnitude relation between I6 and I7 is not clear (I5, I6 and I7respectively represent currents at the DC/DC converters 5, 6 and 7. Thesame holds true in the following).

[0075] In step S46, stopping commands are executed at one time from theC/U 8 to the DC/DC converters 5 to 7.

[0076] In step S47, first, a starting command is executed from the C/U 8to the DC/DC converter 6. A current of the DC/DC converter 6 at thistime is detected by the current detecting means 15, and the current issent to the C/U 8. Then, the DC/DC converter 7 is started after a fixedperiod (about 1 sec.). A current of the DC/DC converter 7 at this timeis detected by the current detecting means 16, and the current is sentto the C/U 8. Then, the DC/DC converter S is started after a fixedperiod (about 1 sec.). A current of the DC/DC converter 5 at this timeis detected by the current detecting means 14, and the current is sentto the C/U 8.

[0077] In step S48, based on the current changes detected in step S47, amagnitude relation in current characteristics among the DC/DC converters5 to 7 is obtained. (I6>I7, I5>I7, and I5>I6).

[0078] In step S49, stopping commands are executed again from the C/U 8to the DC/DC converters 5 to 7.

[0079] In step S50, first, a starting command is executed from the C/U 8to the DC/DC converter 7. A current of the DC/DC converter 7 at thistime is detected by the current detecting means 16, and the current issent to the C/U 8. Then, the DC/DC converter 5 is started after a fixedperiod (about 1 sec.). A current of the DC/DC converter 5 at this timeis detected by the current detecting means 14, and sent the current tothe C/U 8. Then, the DC/DC converter 6 is started after a fixed period(about 1 sec.). A current of the DC/DC converter 6 at this time isdetected by the current detecting means 15, and the current is sent tothe C/U 8.

[0080] In step S51, based on the current changes detected in step S50, amagnitude relation in current characteristics among the DC/DC converters5 to 7 is acquired. (I5>I7, and I5>I6, but a magnitude relation betweenI6 and I7 is not clear).

[0081]FIG. 9 shows a relation between the operation of the DC/DCconverter and the change of current in steps S44 to S50.

[0082] In step S52, based on the results of steps S25, S28 and S31, amagnitude relation in current characteristics (I5>I6>I7 in this example)among the three DC/DC converters 5 to 7 is obtained. Then, a startingsequence after normal starting time is set in the order of small currentcharacteristics (DC/DC7→DC/DC6→DC/DC5 in this example).

[0083] Steps S53 and S54 are similar to steps S6 and S7 of the firstembodiment, respectively.

[0084] Therefore, a frequency of use of a DC/DC converter having a smallcurrent characteristics becomes large at time of starting. However, whena load becomes large, and the plurality of DC/DC converters areoperated, a load of the DC/DC converter having a small currentcharacteristics becomes small, whereby deviation in frequencies of usecan be canceled.

[0085] In the third embodiment, current characteristics of the DC/DCconverters are measured after they are mounted on the vehicle. However,the measurement is not limited to this. For example, currentcharacteristics of the DC/DC converters may be measured before they aremounted on the vehicle, and then a starting sequence may be storedbeforehand in the C/U 8 based on a magnitude relation of the currentcharacteristics. In such a case, the steps S41 to S52 can beabbreviated.

[0086] (Fourth Preferred Embodiment)

[0087] A hardware configuration of a fourth embodiment is similar tothat of the third embodiment. Description of portions common to those ofthe previous embodiments will be omitted.

[0088] In the present embodiment, a predetermined starting sequence ischanged based on cumulative loads of DC/DC converters.

[0089]FIG. 10 is a flowchart showing control in outline.

[0090] In step S70, determination is made so as to whether this processis the first process or not to pass through the step S70 after ION ON.If it is the first process, in step S71, determination is made as towhether the IGN ON is the first or not (after vehicle manufacturing). Ifit is the first process, then in step S72, a starting sequence is set toDC5→DC/DC6→DC/DC7. Here, this sequence has no special significance, andan optional sequence may be set.

[0091] Steps S73 and S74 are similar to steps S6 and S7 of the firstembodiment. Namely, the number of DC/DC converters to be operated isdecided according to loads states (i.e., demanded electric power) of theauxiliary loads 11 and 12. Moreover, the DC/DC converters are startedaccording to the set pattern of the starting sequence.

[0092] In step S75, currents on operation of the DC converters 5 to 7are detected by the current detecting means 14 to 16 respectively, andthe current is sent to the C/U 8. In the C/U 8, a cumulative value ofeach of the sent-in currents (i.e., a cumulative current) is calculated,and memorized. This cumulative current corresponds to a cumulative loadof each of the DC converters. The cumulative current is also memorizedin the C/U 8 after IGN OFF. In next IGN ON, the process proceeds fromstep S71 to step S76.

[0093] In step S76, the memorized cumulative currents of the respectiveDC/DC converters are compared with one another, thereby setting astarting sequence in the order of small cumulative currents at thistime.

[0094] Accordingly, frequency of use of each of the DC/DC converters canbe made uniform.

[0095] The present disclosure relates to subject matters contained inJapanese Patent Application No. 2001-305980, filed on Oct. 2, 2001, thedisclosure of which is expressly incorporated herein by reference in itsentirety.

[0096] While the preferred embodiments of the present invention havebeen described using specific terms, such description is forillustrative purposes. It is to be understood that the invention is notlimited to the preferred embodiments or constructions. To the contrary,the invention is intended to cover various modifications and equivalentarrangements. In addition, while the various elements of the preferredembodiments are shown in various combinations and configurations, whichare exemplary, other combinations and configurations, including more,less or only a single element, are also within the spirit and scope ofthe invention as defined in the following claims.

INDUSTRIAL APPLICABILITY

[0097] As described above, according to the present invention, theamounts of electric power used by the loads are combined, and the DC/DCconverters are started by a predetermined starting sequence. Therefore,a starting sequence is set to prevent concentration of loads, wherebyloads of the plurality of DC/DC converters can be dispersed.Accordingly, a system life can be prolonged without any one of theconverters shortened in life.

1. A replenishing power supply system for supplying electric power to a load, the replenishing power supply system comprising: a main power supply; a plurality of DC/DC converters for converting the electric power from the main power supply and outputting the electric power; and an auxiliary battery for charging the electric power converted by the plurality of DC/DC converters, wherein the plurality of DC/DC converters are connected in parallel, wherein the number of DC/DC converters to be started is changed according to an amount of the electric power used by the load, and wherein based on a predetermined starting sequence, the DC/DC converters are started in order.
 2. The replenishing power supply system according to claim 1, wherein the predetermined starting sequence is changed by a regulated sequence.
 3. The replenishing power supply system according to claim 1, wherein the predetermined starting sequence is set based on a voltage-current characteristics of each of the DC/DC converters.
 4. The replenishing power supply system according to claim 3, wherein the predetermined starting sequence is set based on a voltage characteristics of each of the DC/DC converters.
 5. The replenishing power supply system according to claim 3, wherein the predetermined starting sequence is set based on a current characteristics of each of the DC/DC converters.
 6. The replenishing power supply system according to claim 1, wherein the predetermined starting sequence is changed based on a cumulative load of each of the DC/DC converters. 